This application is related to a provisional patent application filed on the same date as the instant provisional application, entitled Method For Manufacturing A Bipolar Junction Transistor.
This invention relates generally to the field of semiconductor devices and, more specifically, to a method for manufacturing a bipolar junction transistor.
Semiconductor devices are used for many applications, and one component used extensively in semiconductor devices is a transistor. There are many different types of transistors, including bipolar junction transistors. Bipolar junction transistors (xe2x80x9cBJTsxe2x80x9d) are used to make other types of transistors and devices, such as a complementary metal oxide semiconductor (xe2x80x9cCMOSxe2x80x9d), which utilizes NPN and PNP BJTs for increased performance.
Many factors are considered in manufacturing BJTs. One such factor is dopant diffusion. Dopant diffusion determines how a particular BJT performs and is influenced by such factors as dopant type, implantation energy, the type of material the dopant is implanted in, and the time and temperature of any annealing processes. Problems arise when too much, or too little, diffusion of dopants occurs. For example, depending on the type of BJT being manufactured, any of the above factors can cause undesirable base concentrations and base widths as well as undesirable emitter widths. Accordingly, these undesirable attributes can hurt BJT performance, including reduced speed, band-to-band tunneling, and less than optimal linearity. Therefore, semiconductor manufacturers desire methods of manufacturing BJTs that control the formation and diffusion of dopants so that the performance of BJTs is improved.
The challenges in the field of semiconductor devices continue to increase with demands for more and better techniques having greater flexibility and adaptability. Therefore, a need has arisen for a new method for manufacturing a bipolar junction transistor.
In accordance with the present invention, a method for manufacturing a bipolar junction transistor is provided that addresses disadvantages and problems associated with previously developed methods.
According to one embodiment of the invention, a method for manufacturing a bipolar junction transistor includes implanting a first base dopant in a semiconductor substrate, forming an epitaxial layer outwardly from the semiconductor substrate, and forming a dielectric layer outwardly from the epitaxial layer. The method also includes etching a first portion of the dielectric layer to form an emitter region, forming an emitter polysilicon layer on the semiconductor substrate, and implanting an emitter dopant in the emitter polysilicon layer. The method further includes etching a portion of the emitter polysilicon layer and a second portion of the dielectric layer to form an emitter polysilicon region having sidewalls, forming nitride regions on the sidewalls, and implanting a second base dopant in the semiconductor substrate. After implanting the second base dopant, an annealing process is performed for the semiconductor substrate to form an emitter and a base.
Embodiments of the invention provide numerous technical advantages. For example, a technical advantage of one embodiment of the present invention is the reduction of the base peak concentration at the polysilicon-to-silicon interface, thereby increasing performance of bipolar junction transistors. Another technical advantage of one embodiment of the present invention is that optimizing the base doping density profile substantially reduces or eliminates the emitter-base band-to-band tunneling problem in bipolar technology. An additional technical advantage of the present invention is that a resulting narrow base width increases the operating frequency of bipolar junction transistors.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.